A device that recognizes MIDI Note On messages must be able to recognize both a real Note Off as well as a Note On with 0 velocity (as a Note Off). There are many devices that generate real Note Offs, and many other devices that use Note On with 0 velocity as a substitute.
I add debug messages to debug midi messages filtering "clock" message to avoid flood.
fix #235 As Midi specification said :
I add debug messages to debug midi messages filtering "clock" message to avoid flood.